Physiology of Sun and Shade Plants

Green plants are able to use the solar radiation from 400 to 700 nanometers in the process of photosynthesis. This range of radiation is called as Photosynthetically Active Radiation (PAR). Among various abiotic factors, light has a major influence on the life of land plants. Based on the requirement of light, plants are classified as sun and shade plants with various integrates in between. The concept of sun-requiring species and shade-requiring species has been adopted for plants that need high irradiance and intense shading, respectively, for their growth and development. Differing in their morphology and physiology, shade plants have thin leaves, more leaf area and more chlorophyll content than sun plants. Sun leaves are thicker than shade leaves because they develop longer palisade cells or an additional layer of palisade cells. In addition to this, shade chloroplasts are larger than those present in sun plants. Sun plants have small light harvesting complex with large number of reaction centers whereas shade plants exhibit large LHC’s with less number of reaction centers. In general photosynthesis in shade plants is saturated at low light levels whereas sun plants shows increased photosynthetic rate at higher light saturation point. Adjustment to leaf physiology is apparently integral features in the process of acclimating to contrasting light environment.